In an existing COG (Chip On Glass) type of liquid crystal panels, the interval of lead wires at the connection between a drive chip bonded within a bond region of a glass substrate and the substrate is becoming increasingly small, e.g. about 15 μm. Accordingly, the interval of pins of a test group of pins is required to reach this level if an open test is performed to these lead wires in a conventional full contact mode. However, the interval of pins of the existing group of pins is at least about 30 μm, and the open test of lead wires can thus not be well implemented in the full contact mode. Furthermore, any test mode having a connection port contacted directly with a wiring terminal in the bond region generally has a high possibility of puncturing the lead wires, resulting in defects and a waste of materials.
Therefore the open test of lead wires of a COG liquid crystal panel is often performed in a shorting bar switching test mode in the prior art. That is, a display drive signal for the liquid crystal panel is provided by using a shorting bar circuit disposed at sides of the panel in order to carry out the test by observing light emitting; and at the mean time, the shorting bar circuit is switched between an active state and an inactive state in a switch controlled manner. However, for some reasons such as some of products being limited by the size of design space when designed, signal lines of the shorting bar circuit are not capable of passing through a region in which the above described lead wires are located and a fan-out region of the liquid crystal panel, so that the open of the wirings within these regions could not be detected in a shorting bar switching test mode if happens.
Accordingly, for the above described COG panel, the full contact mode would have a great amount of pin misses (i.e. some of the lead wires or wiring terminals within the bond region are not contacted with the pins) because the interval of pins is not small enough. Also, the lead wires would be punctured in the full contact mode, causing defects and a waste of materials. Furthermore, the open of lead wires occurred within some of the regions cannot be detected in the shorting bar switching test mode as described above, which fails to achieve a test effect. For the above reasons, a test for the open of lead wires of such a COG panel cannot be implemented in any existing conventional test modes.